Approximately 300 million individuals, nearly the population size of the United States, suffer some form of depression throughout the world. Depression is characterized by feelings of sadness, hopelessness, anxiety, irritability, appetite changes, sleep pattern changes and sometimes, suicidal thoughts.

While depression may occur at any time of life, antepartum depression, or depression during pregnancy, is particularly common. This form of depression occurs in about 14-23% of pregnant women, according to the American Congress of Obstetricians and Gynecologists. Due to the major hormonal and bodily changes that occur during pregnancy, women are more susceptible to depression during this time. Additionally, antepartum depression has been associated with adverse outcomes in both the mother and infant, including postpartum depression, low birth weight and preterm birth.

Vitamin D has been a subject of exploration in relation to depression. Recent research suggests vitamin D may help treat depression symptoms. Additionally, a recent randomized controlled trial found that improving vitamin D status during late pregnancy reduced depressive symptoms in women after giving birth. However, research has yet to analyze the effect of vitamin D status on depression throughout the nine months of pregnancy. Therefore, researchers from this study explored the relationship between 25(OH)D status and depressive scores in pregnant women during the first, second and third trimester.

The researchers included 179, 156 and 128 women from Rio de Janeiro, Brazil during the first, second and third trimester, respectively. Fasting blood draws were taken during each trimester to determine vitamin D status. Depression was also measured at each trimester by the Edinburgh Postnatal Depressive Scale (EPDS), with higher scores indicating more severe depression. Researchers also adjusted for potential confounding variables such as marital status, per-capita family, smoking, alcohol intake, skin color, physical activity before pregnancy, planned pregnancy and season of recruitment for the study.

This is what the researchers found:

20.1%, 14.7% and 7.8% of the women experienced depressive symptoms during the first, second and third trimesters, respectively.

Every 0.4 ng/ml increase in vitamin D levels during the first trimester was associated with a 2% decrease in depressive symptoms (p=0.047).

The researchers concluded:

“Women with higher concentrations of 25(OH)D in early pregnancy were associated with lower odds of depressive symptoms during pregnancy, after adjustment for relevant confounders.”

They continued:

“There is a high interest in modifiable risk factors for the prevention or treatment of depression. Improving vitamin D status among pregnant women may be a cost-effective strategy.”

It is important to note that several of the women participating in the study had a history of depression. This suggests the possibility of reverse causality, because these women would have likely spent less time outside in the sun, putting them at risk for vitamin D deficiency. Despite this, there were several strengths to this study. First, the longitudinal design allowed for variables to be measured over time, giving a more accurate indication of the association between vitamin D and depression. Additionally, several confounding variables were adjusted for.

This study provided further insight into the relationship between vitamin D and depression. The researchers called for randomized controlled trials to determine if there is a causal relationship between vitamin D status and depression during pregnancy.